Direct coating method

ABSTRACT

The invention relates to a method for producing self-solidifying film forming substances from initial liquid substances in a device designed for this purpose and to a corresponding device. The inventive method consists in coating an inert continuously advancing carrier in the form of the part of said device with initial substances ( 7, 13 ). A dosing device ( 25 ) makes it possible to adjust the thickness of said initial substances for coating the carrier. The coated carrier conveys a substance layer ( 23 ) to a drying device ( 30 ). The dried substance layer separates itself from the carrier or is removed therefrom. Said method makes it possible to produce self-solidifying film-forming gelatinous substances exhibiting a low material thickness variation from initial liquid substances.

The invention relates to a method for producing film-like solidifyingsubstances from initially free-flowing starting substances in a suitablyconfigured apparatus, and corresponding apparatus.

The substances are, for example, pharmaceutical preparations whichsolidify from an originally free-flowing state. They may, for example,contain pharmaceutical active ingredients and/or flavorings. As theydry, these materials may solidify in jelly style, for example thickenand solidify. The film-like end product may in this case be elasticallyor plastically deformable.

DE 101 21 972 A1 has disclosed a drying chamber in which a free-flowingsubstance which has been applied to a paper-like, polyethylene-coatedcarrier material in web form, is dried. This paper-like carrier materialis expensive and can only be used once. Moreover, it brings with it therisk of infestation with insects or other impurities.

U.S. Pat. No. 4,562,020 has disclosed a method for dryingglucose-containing solutions on an endless plastic belt. The thicknessof the film which becomes detached from the plastic belt after it hasdried varies considerably.

U.S. Pat. No. 4,306,059 has disclosed a method for producing a film inwhich a liquid substance is applied to a preheated, chromium-platedroller.

Therefore, the present invention is based on the object of developing aninexpensive method and an apparatus for producing film-like substanceswhich solidify in jelly-like form with only minor deviations in thematerial thickness from free-flowing starting substances.

This problem is solved by the features of the main claim. For thispurpose, a continuously moving, inert carrier which is part of theapparatus is coated with the starting substances. The thickness of thestarting substances which coat the carrier is set by means of a meteringapparatus. The coated carrier then moves the layer of substance througha drying device. After the drying operation has ended, the driedsubstance layer becomes detached or is detached from the carrier.

During the method, the inert carrier comes into contact with thestarting substances without reacting with them. During this contact, thematerial of the carrier is not attacked or changed either chemically orphysically or biologically.

The carrier may, for example, be a rotating roller or a continuous,endless belt, to which the starting substance is applied or whichreceives the starting substance. After the substance has dried on thecarrier, it becomes detached or can be detached from the carrier. Thecarrier itself does not require any further treatment and canimmediately be reused to receive further starting substances.

The thickness of the coating of the carrier is set by means of ametering apparatus. The metering apparatus may, for example, be anadjustable outlet opening of a reservoir, a metering roller, etc. If ametering roller is used, its distance from the inert carrier isadjustable, for example. A coating of at least approximately constantthickness is produced on the inert carrier. The end product has auniform thickness. The deviations in the thickness in the longitudinaland transverse directions of the extent of the film are slight.

This method does not entail the use of any disposable material whichwould have to be purchased at high cost and then disposed of againfollowing the production process. This makes the method inexpensive inparticular in the case of intensively used manufacturing installations.

Further details of the invention will emerge from the sub-claims and thefollowing description of diagrammatically depicted embodiments. In thedrawing:

FIG. 1 shows a section through an apparatus for producing film-likesubstances;

FIG. 2 shows a section through an apparatus having a different substancebath.

FIG. 1 shows a section through an apparatus for producing film-likesubstances (7, 43) from a free-flowing starting substance (7, 13).

The apparatus is arranged in a fixed outer housing (1) and comprises anapplication point (10), a carrier (20), a drying device (30) and aseparation region (40).

At the application point (10), the free-flowing starting substance (7,13) is applied to the carrier (20) as a substance layer (7, 23) meteredby means of a metering apparatus (25). The substance layer (7, 23) isdried in the drying device (30). In the separation region (40) thesubstance layer becomes detached from the carrier (20) in the form of afilm or is detached from the carrier and then fed as a film-likesubstance (7, 43) for further processing.

The application point (10) comprises, for example, a feed line (11),which is used to move a free-flowing starting substance (7, 13) whichhas been made up into a reservoir (12) arranged within the housing (1).The free-flowing starting substance (7, 13) may be enriched, forexample, up to a solids content of 40%.

As an alternative to using a feed line (11), it is also possible for thestarting substance (7, 13) to be made up directly in a reservoir (12),which is then inserted into the housing (1). It is also conceivable forit to be made up in a separate container which is in communication withthe reservoir (12).

The carrier (20) is, for example, a roller (20) made from a metallicmaterial which is resistant to chemical reactions and is physicallydurable. This material may, for example, be a corrosion-resistant steel.

The roller (20) is, for example, a hollow cylinder. Its externaldiameter is, for example, approximately three meters, and its lengthtransversely to the delivery direction (5) is approximately 1.8 meter.At its end side is a drive unit (not shown here). This comprises, forexample, an electric motor which, by way of example, drives the roller(20) via a transmission with a high step-up ratio.

The interior (21) of the roller (20) may have a heating-gas opening(24), which can be used, for example, to supply heated air forinternally heating the roller (20).

The drying device (30) comprises a compressor (37) and a heater (notshown) as well as a distribution manifold (31) which is arranged betweenthe outer housing (1) and an inner housing (2). By way of example fivenozzles (32-36) are arranged in the inner housing.

Each of these nozzles (32-36) is oriented centripetally with respect tothe roller (20), so that the individual nozzle (32-36) is in each casepositioned perpendicular to an imaginary tangential plane on the surface(22) of the roller. The length of each individual nozzle (32-36)transversely with respect to the direction of movement (5) at leastapproximately corresponds to the length of the roller (20). The airdistribution manifold (31) and the nozzles (32-36) forcibly guide adrying medium from the compressor at least onto the substance layer (7,23) and then discharge it into a vent opening (38). From here, thedrying medium can be fed back to the compressor (37), for example viadevices for humidifying or dehumidifying the drying medium.

The air distribution manifold (31) may be of multi-part design. By wayof example, each of the nozzles (32-36) can be supplied with speciallytreated drying medium. The drying medium which flows through theindividual nozzles (32-36) can then, for example, have a differentvolumetric flow and/or a different temperature.

The separating region (40) comprises, for example, a separatingapparatus (41) for peeling the substance layer (7, 23) off the roller(20) and, for example, a guide roller (42). The separating apparatus(41) is in the form, for example, of a blade which includes an acuteangle with an imaginary tangential plane on the surface (22) of theroller (20).

At the start of production of the film-like substance (7, 43), thereservoir (12) is filled with free-flowing starting substance (7, 13)sufficiently far for the surface (22) of the roller (20) to be incontact with or submerged below the surface (14) of the startingsubstance (7, 13).

After the drive unit has been switched on, the roller (20) rotates, forexample, at a constant rotational speed. The circumferential velocity ofthe surface (22) of the roller (20) is then, for example, 10 m/min.

The free-flowing starting substance (7, 13) is picked up from thereservoir (12) by the rotating roller (20) by wetting the latter, sticksto the roller as a coating and is carried along by the roller (20).

The metering apparatus (25) is arranged in the region of the applicationpoint (10). This metering apparatus comprises a metering or strippingroller (26), for example a doctor roller (26). The distance between thisdoctor roller (26) and the roller (20) is adjustable. This doctor roller(26) is used to distribute the starting substance (7, 13) which has beenpicked up uniformly over the surface (22) of the roller (20). Excessstarting substance (7, 13) by way of example drips off a doctor grateand flows back into the reservoir (12).

Depending on the length of the roller (20), the metering roller (26) maybe supported at one or more points by means of bearings. This preventsinaccuracies in the thickness of the substance layer (7, 23) caused bythe metering roller (26) sagging. A parallel arrangement of a pluralityof metering rollers (26) is also conceivable.

The remaining coating of the roller (20) is a substance layer (7, 23)with a constant thickness of, for example, 0.3 mm which adheres to theroller (20). As the rotation of the roller (20) continues, the substancelayer (7, 23) is moved into the drying device (30). The drying device isseparated from the reservoir (12) for example by a horizontal housingwall.

In the drying device (30), drying medium, for example dehumidified air,which has been heated to, for example, 95° C. is passed into thedistributor manifold (31) by the compressor. The drying medium flowsthrough the nozzles (32-36) perpendicularly onto the substance layer (7,23) and if appropriate to a collector. In the process, moisture iswithdrawn from the substance layer (7, 23) so that the latter is driedto a residual moisture content. The substance layer (7, 23) in theprocess solidifies in jelly-like form.

If the nozzles (32-36) are supplied separately, the drying operationcan, for example, be controlled in such a way that, for example, moremoisture is withdrawn in the region of the first nozzle (32) than in theregion of the last nozzle (36) or vice versa.

As the moisture content of the substance layer (7, 23) decreases, by wayof example its adhesion to the roller (20) decreases. After the dryingoperation has ended, below a substance-specific residual moisturecontent, the substance layer (7, 23) becomes detached from the roller(20). If appropriate, the start of the substance layer (7, 23) can belifted off the roller (20) using the separating apparatus (41). Thesubstance layer (7, 23) which has been lifted off the roller (20) is nowa film-like substance (7, 43) which is conveyed to the winding roller(46) with the aid of the guide roller (42). From the winding roller(46), the film-like substance (7, 43) is passed for further processing,for example for cutting or dividing into lengths.

The roller (20) may be internally heated. It is in this way possible toaccelerate the drying process of the substance (7, 23) on the roller(20) and to improve the way in which the film-like substance (7, 43)becomes detached from the roller (20).

The rotational speed of the roller (20) may be fixed or adjustable. Byway of example, in the case of an installation on which differentsubstances (7) are produced, it is possible to set specificcircumferential velocities for each substance (7). The film-likesubstance (7, 43) then in each case has the required chemical andphysical properties.

FIG. 2 shows an apparatus with a different substance bath. The reservoir(12) is in this case arranged in the fourth quadrant of the roller (20).The reservoir (12) is open toward the roller (20), so that thefree-flowing starting substance (7, 13) bears directly against theroller (20). The bath of the starting substance (7, 13) is shallow, sothat the starting substance (7, 13) has only a short residence time inthe reservoir (7, 13) between flowing out of the feed line (11) andbeing picked up by the roller (20). This means that there is only a lowrisk of volatile constituents of the starting substance (7, 13)evaporating, and also reduces the risk of the starting substance (7, 13)decomposing.

LIST OF DESIGNATIONS

-   1 Outer housing-   2 Inner housing-   3 Housing aperture-   4 Housing aperture-   5 Direction of movement-   7 Substance-   10 Application point-   11 Feed line-   12 Reservoir-   13 Free-flowing starting substance-   14 Surface of (13)-   15 Coating-   20 Carrier, roller-   21 Interior of (20)-   22 Surface of (20)-   23 Substance layer-   24 Heating gas opening-   25 Metering apparatus-   26 Metering roller, stripping roller, doctor roller-   30 Drying device-   31 Distribution manifold-   32-36 Nozzles-   37 Compressor-   38 Vent opening-   40 Separating region-   41 Separation apparatus-   42 Guide roller-   43 Film-like substance-   46 Winding roller

1. A method for producing film-like solidifying substances (7, 43) frominitially free-flowing starting substances (7, 13) in a suitablyconfigured apparatus, in which a continuously moving, inert carrier(20), which forms part of the apparatus, is coated with the startingsubstances (7, 13), in which the thickness of the starting substances(7, 13) which coat the carrier (20) is set by means of a meteringapparatus (25), in which the coated carrier (20) moves the substancelayer (7, 23) through a drying device (30), and in which the driedsubstance layer (7, 43) becomes detached or is detached from the carrier(20).
 2. The method as claimed in claim 1, characterized in that aroller (20) is coated with the starting substances (7, 13).
 3. Themethod as claimed in claim 2, characterized in that the roller (20)rotates at a constant circumferential velocity.
 4. The method as claimedin claim 2, characterized in that the roller (20) is internally heated.5. The method as claimed in claim 3, characterized in that the rotatingroller (20) comes into contact with the free-flowing starting substance(7, 13) in a reservoir (12), picks up the free-flowing startingsubstance by being wetted with it, and then excess starting substance(7, 13) is stripped off by means of a metering apparatus (25).
 6. Themethod as claimed in claim 1, characterized in that a drying medium ismoved forcibly within the drying device (30) so that it flowsperpendicularly onto the coated carrier (20).
 7. The method as claimedin claim 6, characterized in that the drying medium which flows in ispassed through at least two nozzles (32-36) oriented perpendicular tothe carrier (20).
 8. The method as claimed in claim 7, characterized inthat the volumetric flow and/or the temperature of the drying mediumwhich flows in from at least two nozzles (32-36) differs.
 9. Anapparatus for producing film-like, solidifying substances fromfree-flowing starting substances which comprises an application pointfor applying the starting substances to a moveable carrier, a meteringapparatus for setting the thickness of the starting substances whichcoat the carrier, and a drying device for drying the startingsubstances, characterized in that the carrier (20) consists of ametallic material which is resistant to chemical reactions and isphysically durable.
 10. The apparatus as claimed in claim 9,characterized in that the carrier is a roller (20).
 11. The apparatus asclaimed in claim 9, characterized in that it comprises a housing (1, 2)in, which a drying medium is fed forcibly perpendicular to the carrier(20) and is discharged transversely with respect to the direction ofmovement (5).
 12. The apparatus as claimed in claim 11, characterized inthat the drying medium which flows in is passed through at least twonozzles (32-36) which are oriented perpendicular to the carrier (20),the length of the individual nozzle transversely to the direction ofmovement (5) at least approximately corresponding to the length of thecarrier (20) transversely to the direction of movement (5).